Method of and machine for grinding a roll

ABSTRACT

A method and machine for grinding a rolling mill roll in which the grinding wheel is rotated against the working surface of the rotating mill roll and is displaced back and forth longitudinally along this surface and simultaneously or subsequently the surface is examined for defects by sensors capable of evaluating the geometry of the roll surface. The measured results are compared with stored images or data representing defects in the surface and measured surface defects are compared with the stored data and if they exceed a certain threshold or defect tolerance, an appropriate output is provided by the grinding machine.

FIELD OF THE INVENTION

My present invention relates to a method of grinding a roll on aroll-grinding machine in which the working surface of the roll, i.e. thesurface which is intended to bear upon the rolled workpiece, is groundby a grinding wheel or disk. The invention also relates to theroll-grinding machine for use with that machine.

BACKGROUND OF THE INVENTION

In the production of strip and metal foil, it is a current practice toroll the workpiece until a certain strip thickness and certain surfacequality is obtained. In order to ensure the quality of the rolled metalstrip, the metal strip is scanned in the last production stage as asensor system and surface defects on the strip are detected. The scannedimages can be compared with previously stored defect images and thequality of a particular length of the strip can be established, e.g. asa function of a number defects or the nature of the defect.

That portion of the strip which may be classified as defective, can thenbe cut out and discarded.

For the scanning of the strip, commercially available sensors are used.Equally known are evaluating systems which can include image recognitionsoftware and analytical software for determining defect frequency orwhich can weigh particular defects relative to others. It is known, inthis connection that a considerable part of the surface defects found inmetal strip have their origins in defects in the working surface of theroll. It is important to distinguish between those defects in thesurface of the roll which arise in the course of the rolling process andthus which are already present at the time of manufacture of the roll.

In the machining of the roll it is known to provide a largely automatedapproach in which the high precision of the surface geometry of the rollis ensured by a grinding process, usually the last grinding step in thecase of a new roll or even in the case of a remachined used roll beforeit is mounted for use anew in the rolling mill. The roll grinding isusually subjected to a form of quality control by for example a visualinspection of the roll surface by trained personnel seeking to detectthe presence of any defects arising from the machining operation.

This kind of quality control is a strain on personnel since there aremany possible defects which can be present and the result of the qualitytesting is basically very subjective and may depend on the state of thequality control personnel and their experience.

A nondetected defect arising during the grinding process in the roll maybe only found out too late during the rolling of strip or foil. Althoughusually that detection occurs very early on in the initial use of theroll, generally in the first few hundred meters of rolled strip orafter, say 3 to 4 minutes of production time.

As a rule, therefore, overlooked or erroneously classified defects inthe grinding of the roll clan have very negative effects on theefficiency of the manufacturing processes for rolled strip or foil.

OBJECTS OF THE INVENTION

It is, therefore, the principal object of the invention to provide aroll-grinding process or method and roll-grinding machine for practicingthat method which can avoid the foregoing drawbacks.

More particularly, it is the object of the invention to provide animproved method of grinding a roll for producing strip for foil which isfree from the subjectivity of inspection and process-control previouslycarried out and thus which can allow greater efficiency and less wastein the rolling process for the production of strip and foil.

Still another object of the invention is to provide a roll-grindingmethod and machine, especially for rolls used in the production ofrolled strip and foil, whereby higher quality surface-ground rolls canbe obtained.

SUMMARY OF THE INVENTION

These objects are attained, in accordance with the invention, in amethod of grinding a roll which comprises the steps of:

-   -   (a) mounting a roll for the rolling of workpieces in a        roll-grinding machine having a grinding wheel engageable with        said roll and grinding a working surface of said roll therewith;    -   (b) subsequent to or simultaneously with the grinding of the        working surface of the roll, scanning the working surface of the        roll for defects with at least one sensor on the machine capable        of recognizing the geometry of the working surface;    -   (c) then automatically evaluating results of the scanning in        step (b) by automatically comparing the results with stored data        as to qualities of said surface; and    -   (d) automatically outputting information as to the evaluation in        step (c).

The roll grinding machine for that purpose can then comprise:

-   -   a machine structure for receiving and rotating a roll for the        rolling of workpieces;    -   a grinding wheel engageable with the roll for grinding a working        surface of the roll;    -   at least one sensor capable of recognizing the geometry of the        working surface for scanning the working surface of the roll for        defects subsequent to or simultaneously with the grinding of the        working surface of the roll;    -   circuitry connected to the sensor for automatically evaluating        results of the scanning by automatically comparing the results        with stored data as to qualities of the surface; and    -   a device connected to the circuitry for automatically outputting        information as to the evaluation.

With the method of the invention, initially the roll surface, referredto herein as the working surface of the roll and the surface whichengages the workpiece when the roll is mounted in a mill stand, isground with at least one grinding wheel or disk in a roll-grindingmachine in which the grinding wheel or tool is moved along the roll orthe roll is moved relative to a grinding head so that the grindingaction, with rotation of the roll, will cover the entire workingsurface.

Simultaneously therewith or subsequently, the ground surface of the rollis scanned with at least one sensor capable of recognizing the geometryof the roll surface and detecting defects thereon.

Then the results of that scan or test of the roll surface isautomatically evaluated at least in part by an automatic comparison ofthe result of that scan with stored data as to the quality andcharacteristics of the desirable roll surface.

Finally information as to the result of that comparison is outputted,also automatically.

Thus with the invention in the roll-grinding machine itself, there is anexamination of the ground roll surface with respect to its geometry,namely the surface characteristics and microgeometry which may besignificant for the rolling properties of the roll and quality of themetal strip to be produced therewith.

The defects can be optically detected since they will representdeviations from the ideal geometry represented by the data stored inmemory and with which the comparison is made. The invention enables,from the multiplicity of known possible and different surface defects,specific defects to automatically be recognized and classified so thatfor any further processing steps, automatically determined grindingparameters can be altered and such that in the subsequent grindingoperations those defects can be removed.

So that the examination can be effected as rapidly and as economicallyas possible and will also be free from subjective input, the evaluationis carried out based on comparison with a data base and storedinformation in a type of expert system in which the evaluation is madewithout input from the operating personnel.

According to a feature of the invention, the stored data can be qualitysetpoint data as to the rolled surface and/or typical defect data. Thepreferably typical defect data can be stored and compared with theresults of the scan to see if any defect represented by the stored datais present. Similarly it is possible to register properties of thesurface in the data base which represents the desirable or setpointproperty, against which a comparison is made to determine if a defect ispresent.

Usually the sensor carrying out the inspection of the roll will be anoptical sensor.

The information outputted in accordance with the invention can include awarning signal which can indicate an evaluation result showing adeviation of the inspected roll surface from stored data representing asatisfactory surface which exceeds a predetermined and stored tolerance.That permits certain tolerances within which the geometrical data fromthe roll surface can vary. When these tolerances are exceeded there is acorresponding warning which makes it possible for personnel to reacteven prior to the development of significant machining defects in theroll surface or at a time when any such defect can be ameliorated atrelatively low cost.

The outputting of information can be effected graphically on a machinecabinet. Alternatively or in addition the information can be madeavailable in a printed form which has the advantage that it can providea written documentation of the roll quality.

It has been found to be advantageous to provide a sensor which is orincludes a laser and/or a camera, especially a digital camera.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features, and advantages will become morereadily apparent from the following description, reference being made tothe accompanying drawing in which:

FIG. 1 is a perspective view of a roll grinding machine;

FIG. 2 is a perspective view of an alternative roll grinding machine forcarrying out the method of the invention;

FIG. 3 is an elevational view of a roll grinding machine showing theroll in place and a flow diagram of the inspection, evaluation andoutput of the roll grinding process;

FIG. 4 is another elevational view of the roll grinding machine drawn toa larger scale;

FIGS. 5 a and 5 b are elevational views of a portion of a roll and aradial section of that roll, respectively, showing a defect pattern inthe form of staggered crests;

FIGS. 6 a and 6 b are views similar to FIGS. 5 a and 5 b, respectively,showing a defect pattern produced by machine chatter and in the form ofa faceting of the roll surface;

FIG. 7 is a schematic illustration of a third defect pattern in the formof facets constituted by interruptions and discontinuities in thesurface of the roll in an elevational view of the working surfacethereof;

FIG. 8 is a diagrammatic illustration of a fourth defect image withfaceting as seen in a front elevational view of the roll;

FIG. 9 shows diagrammatically a fifth defect image having the appearanceof wake-like facets as also seen in a front elevational view of he roll;

FIG. 10 a and 10 b are views similar to FIGS. 5 a and 5 bdiagrammatically showing a sixth defect image in the form of acheckerboard pattern;

FIGS. 11 a, 11 b AND 11 c are respectively a front elevational view of apattern of the working surface of the roll, an axial section in oneconfiguration and an axial section in a second configuration,schematically illustrating a seventh defect pattern in the form of atwist;

FIG. 12 schematically shows an eighth defect pattern having atrapezoidal configuration as seen in a front elevational view of theroll;

FIG. 13 is a diagram of a ninth image pattern having the appearance of ashift mark impressed on the roll and seen in a diagrammatic frontelevational view thereof;

FIGS. 14 a and 14 b are diagrammatically a front elevational view of aroll and an axial section therethrough diagrammatically illustrating atenth defect pattern in the form of scratches in the roll surface;

FIG. 15 is a schematic illustration in a front elevation of the rollillustrating an eleventh defect pattern in the form of overlappingscales;

FIGS. 16 a and 16 b are views similar to FIGS. 12 a and 12 bschematically showing a twelfth defect pattern in the form ofclosely-spaced grooves;

FIG. 17 shows a thirteenth defect pattern with a cloudlike appearance ina front elevational view of the working surface of the roll; and

FIG. 18 is a diagram of a fourteenth defect pattern in the form oflarge-area islands with closely delimited regions in a front elevationalview of the working surface of the roll.

SPECIFIC DESCRIPTION

FIGS. 1 and 2 show roll grinding machines 2 upon which a mill roll forthe rolling of strip and foil of metal can be ground. In both of thesemachines, the grinding wheel or disk has been shown at 4.

In the machine of FIG. 1, the ends of the roll can be clamped between ahead stock 10 and a tail stock 11 supporting the roll for rotation on abed 12. The working surface of the roll can be supported on a travelingcarriage 13 and the grinding head 14 can be displaced radially againstthe roll transversely of the axis thereof. The head stock and tail stockcan be positioned with respective servomotors and a drive motor 15 canrotate the roll during the grinding operation. The cross slide or head14 can have an outrigger 16 carrying the sensor which will be describedin greater detail hereinafter and can include an electronic memory fordetecting the defect pattern on the roll.

In the embodiment of FIG. 1, the cross slide or head 14 is mounted on abed 17 which is displaceable along the roll and in the embodiment ofFIG. 2 the grinding head 14 is stationary and the roll is displaceableas represented diagrammatically at 18.

The roll grinding machines themselves insofar as they have beendescribed and without the sensor or automatic inspection facility areconventional in the art and thus need not be described in greaterdetail. In the past, after grinding, e.g. say in one of the machines ofFIGS. 1 and 2, there has been a visual inspection of the surface of therotation roll by an operator of the machine whose conclusions as towhether or not defects might be present was subjective.

With the system of the invention (FIG. 3), as an alternative to thevisual inspection of the surface by the machine operator, the sensor 5is provided to scan the working surface 3 of the roll 1 automaticallyand during the grinding operation or subsequently thereto. The sensor 5in a preferred form is a laser sensor or a camera and, advantageouslycan be a commercially available video or column or row camera responsiveto dark/light differentiations and utilizing appropriate software. Thesensor 5 scans the surface as the roll rotates over the entire length ofthe working surface and can be perpendicular to the surface for thatpurpose. It also may be vertically oriented as shown or otherwiseoriented along the radius to the roll.

The sensor 5 optically scans the working surface 3 of the roll as it isground or following grinding (block 20 of FIG. 3). The measured signalcan optionally be converted to digital signals. In FIG. 4 a holder 8 hasbeen shown by which the sensor is held in the requisite position forscanning the roll surface.

The sensor 5 can be mounted on a measuring unit especially provided forthis purpose on the grinding machine or can be mounted on a part of themachine which normally is provided for measurement purposes. In eithercase the measuring device is provided on a support which can move alongthe roll relative to the roll should the roll be movable along its axis.The scanning of the roll surface may be in helical or spiral patterns asthe roll 1 is rotated. The scanning signals can be stored and in asubsequent step represented by block 21, the signal is evaluated andcompared with a defect library 7 provided to the comparitor included inthe block 21 and as part of the CNC (computer numerical control) unit.The defect library 7 can be a memory for the CNC. Based upon thecomparison, the CNC can control further grinding operationsautomatically.

In addition, since the data in the defect library 7 represents typicaldefect images as for example have been shown in FIGS. 5-18, thecomparison of the scanning signals with the defect library can indicatethe nature of the defect and test the measured defect status todetermine if it exceeds a stored threshold represented by allowedtolerances or known error for example.

The detected defects are likewise classified to determine whether theyfall within the wide range of possible defects and whether, dependingupon the application, they render the roll unsuitable for use. Thedefects which can be determined are not only those which result fromgrinding operations but any which arise from other causes and, ofcourse, may have an effect in the subsequent rolling operation. Thecomparison can result in a graphic display of the defect signal at 22 atthe machine cabinet, a printout of the results and a display of anysignal exceeding the threshold or tolerance limits, including theemission of a warning signal acoustically or visually.

At the machine control cabinet, if a printer is provided, a qualitycertificate can issue (block 23) as may be desirable.

If the determination at 24 shows that the defects on the roll surfacelie within predetermined tolerances, i.e. below a given threshold, thereis an automatic release of the ground workpiece at 25. Should that notbe the case, a locking of the workpiece takes place at 26 so that thesurface of the roll can be reground.

As a consequence, there is an automatic quality test of the ground rollwhile it is on the machine and as a result of the test the roll iseither released or held back for regrinding. The proportion of defectiverolls is thereby significantly reduced.

The described inspection is a component of the grinding process in theroll grinding machine itself and can detect possible defects in thefinished ground roll surface independently from any subjective inputfrom the machine operator. It is also independent of the material of theroll, i.e. whether it is of forged steel or a casting and the resultscan follow a protocol and be documented to serve as a quality warning asto the roll for the production of metal strip and foil.

The analysis of the surface scan for the defect on the surface can useimage recognition software and a computer in the form of a neuralnetwork as is known in the art.

The memory 7 can be used to store images or measured signalsrepresenting images of typical defects found on a surface 3 of the roll.FIGS. 5-18 show only by way of example a number of possible defectimages which have been described in greater detail below and which mayrequire further machining or grinding to eliminate the defect. Thedefects and the Figures themselves should be understood to be purelydiagrammatic and have been intended to show defects only in a stylizedform. In most of these Figures, the pattern of the defect is seen as itmight appear on the surface 3 of the roll 1.

1. Chatter Marks

In FIGS. 5 a and 5 b a front elevational view of the roll 1 and itsworking surface 3 is shown together with a radial section and on whichthe chatter marks 30 can be seen in a helical pattern. The marks canalso be considered to be mouse-tooth or similar patterns. The chattermarks are macrogeometric deviations from a perfect cylindrical shape ofthe roller which close together with a spacing of say 3 to 5 mm and of alength which corresponds to the width of the grinding wheel. Dependingupon the speed with which the wheel sweeps along the length of the roll,the chatter marks can overlap in successive passes as shown in FIG. 5 a.The chatter marks result from vibrations in oscillations which developby themselves between the grinding wheel and workpiece and may originatein nonuniformities in hardness of the grinding wheel and the roll orproblems with the concentricity of the grinding wheel. The energy of theoscillations or vibrations is drawn from the grinding operation itself.Such marks are most pronounced when the grinding wheel is less thanperfectly circular across its entire width. The frequency is in therange of the characteristic frequency of the machine, here meaning thesystem of the grinding spindle, the grinding wheel, the head and/or theroll. The chatter marks can be eliminated by alignment and truing of thegrinding wheel and with fine and superfinish grinding.

2. Faceting

Faceting can also be in the form of strips, lines or transversepatterns. The facets also deviate from the macrogeometric perfection ofthe circular cylinder which is desired and can appear over the entirelength of the working surface, only a part thereof, and usually in apattern which is independent from the width of the grinding wheel. Theylie parallel to the axis of the roll or at a slight inclination theretoand consist usually of fairly machinable rises and depressions in theworkpiece surface.

The facets can be made more visible by bringing the surface in contactwith an inked steel strip or with copper wire, especially after thesurface of the roll has been treated with oil and chalk. The followingtypes of faceting can be distinguished:

2.1 Facets Because of Machine Defects.

In FIGS. 6 a and 6 b an elevational view and a radial section have beenshown of the working surface of a roll having facets because of machinedefects. These facets are the result of oscillations having theirorigins in the drives or drive elements, i.e. motors, gearing, chainsand the like or in friction in which the workpiece may engage in thehead stock or tail stock with a high degree of friction and the patternderives from the characteristic vibration frequency of the workpiece.The more developed they are, the more likely it is that their originsare at the workpiece.

When the excitation force acts only on a part of the workpiece peripheryor part of the workpiece length, facts are generated there and can bepropagated over the entire workpiece (see 2.4 below).

Mainly the source of the disturbance which causes the faceting can beseen in terms of measurements of the dimensions or spacing which agreeshow the defects and when the defects can be alleviated. For example,when the excitation of the defects is seen in terms of an excitationrotation (for example in RPM—revolutions per minute), the relationshipcan be n_(e)=(d_(w)/a)×n_(w). In this relationship, n_(e) is theexcitation speed in RPM, d_(w) is the diameter of the workpiece or rollin mm, n_(w) is the workpiece or roll speed n_(w) in RPM and the facetspacing is given by a in RPM. The excitation speed can also be amultiple of the speed of the roll.

2.2 Faceting as a Consequence of Discontinuities in the WorkieceSurface.

In FIG. 7 facets are shown which are a consequence of discontinuities inthe workpiece or roll surface. Their origin is in the grinding of theinterrupted workpiece surface, for example, by wedge-shaped grooves anddiffer as a consequence of differing grinding pressures. In the case oflongitudinal grinding, they form dislocations in the surface. Thesedefects can be avoided or removed by operating at higher workpiece orroll speeds, sharper abrasives in the grinding wheel and reducedmaterial removal in the finished machining.

2.3 Notch Faceting.

In FIG. 8 notch faceting has been shown schematically. This faceting hasits origin in beveling of the grinding wheel and the action of a beveledgrinding wheel against a hard smooth workiece surface. It occurs whenthe grinding pressure is greater than the centering hydrodynamicpressure in the grinding spindle of the grinding wheel bearing system orthe stiffness of the workpiece or roll. The result is a short durationself-excited vibration.

The problem can be dealt with by making the grinding wheel so hard thata deformation of the grinding wheel cannot occur. Generally the defectcan be removed by further grinding at a different workpiece or rollspeed.

2.4 Drag Faceting.

FIG. 9 shows schematically the defect structure formed by drag faceting.The origin can be the faceting problems arising in 2.1 through 2.3 andcan extend longitudinally over the roll as a result of vibrationsproduced in the grinding wheel from these other sources as the grindingwheel continues to move across the surface. The appearance of suchfaceting is similar to the others and this type of drag faceting arisesprimarily in the case of slender workpieces. The problem can bealleviated by truing the grinding wheel and regrinding with the alteredremoval state and above all at a different rotary speed of the roll andworkpiece and reduced removal rates.

3. Checkerboard Pattern.

FIGS. 10 a and 10 b show a checkerboard pattern on the roll whichrepresents a deviation from the macrogeometric form of the surfaceformed by imparting thereto chatter marks and facts parallel to theworkpiece or roll axis and are interrupted as the grinding wheel movesalong the length of the roll. The origin of these chatter marks isself-excited vibration which has a forced vibration superimposedthereto. It may derive from some imbalance in the grinding wheel or someelectrical defect in the energization of the motor or in the operationof the motor. It can be alleviated or reduced by balance of the grindingwheel and improving the motor operation.

4. Twist.

In FIGS. 11 a to 11 c a defect pattern in the form of a twist has beenshown. The twist can also be formed by spiral or inclined linesimpressed in the surface of the roll. The twist-type of deformation is amicrogeometric deviation from the normal surface configuration. It isusually formed by a pattern of uniformly distributed irregularities ordiscontinuities which may be seen as dark and light regions. The eyedetects the irregularities as parallel lines with a pitch which canassume any value and is dependent on the.

The ratio of the grinding wheel speed to the workpiece or roll speed.

In the spacing of the imaginary twist lines the following relationshipapplies.

The spacing of the twist lines a_(dw) in the circumferential directionof the workpiece and in mm is given by the formulaa_(du)=d_(w)×(n_(w)/n_(s)) whre d_(w) is the workpiece or roll diameterin mm, n_(w) is the workpiece or roll speed in RPM and n_(s) is thegrinding wheel speed in RPM.

The spacing of the twist line in the axial direction in the mm is givenby a_(da)=V_(v)/n_(w) where a_(da) is the spacing of the twist line inthe axial direction, V_(v) is the axial speed of advance of the grindingwheel over the working surface of the roll in mm/min and n_(w) is theworkpiece or roll speed in RPM.

Frequently twist lines of difference sources can be superimposed on oneanother so that one must sort out the twist lines and their dimensionsto determine the causes. Where the nonuniformities run precisely axiallyin the surface, it is difficult to distinguish between such twist linesand the faceting described. The twist line, by contrast with the facetsdo not affect the surface of the roll as significantly and are notmacrogeometric defects causisng significant depressions or projectionsin the surface. The problem with them can be ameliorated by changing theway in which the workpiece twist is rotated, e.g. by providing a rangeof roll speeds. It should be noted that a range of speeds of thegrinding wheel does not produce a uniform roughness on the roll surface.

The following types of twist can be distinguished.

4.1 Twist as a Result of Grinding Wheel Defects.

These twists arise with longitudinal grinding as a result of thedevelopment of a uniform grinding wheel surface or edge and the actionthereof on the workpiece. Possible grinding wheel defects whichcontribute to such twists include nonuniform hardness of the peripheryof the grinding wheel, a damage to the grinding surface or edge, animpact against the cutting edge and the inclination of the workpiece andthe grinding wheel.

The problem can be ameliorated by substituting a grinding wheel ofuniform hardness or eliminating damage to the grinding surface or thecutting edge or truing the wheel. If the problem arises, it can resultin a limited operating period between truing of the wheel.

4.2 Twist from Forced Vibration of the Grinding Wheel Spindle.

As the grinding wheel rotates defects in the grinding wheelspindle-grinding wheel spindle bearings can result in forced vibrationsat a frequency corresponding to the rotating speed of the wheel or amultiple thereof. The system because of nonuniform loading has intervalsof high maximum load followed by intervals of reduced load-producingmarks on the workpiece surface. Such twist defects frequently cannot bedistinguished from twist defects resulting from defects in the grindingwheel surface. The problem can frequently be avoided by frequent checksof the grinding wheel spindle and the spindle bearings.

4.3 Rhombic Patterns.

FIG. 2 shows a defect pattern having a trapezoidal shape. Thetrapezoidal pattern is the special case of a twist which arises inlongitudinal grinding without resetting of the grinding wheel when, forexample, the grinding wheel is moved back and forth along the workpieceand produces a twist in one direction which is superimposed upon thetwist in the other.

The origins and amelioration of this type of defect formation arediscussed in points 4.1 and 4.2 above.

5. Shift Markings

FIG. 13 shows the defect pattern which can arise which shift markings ofthe roll during the grinding operation. In appearance the shift markingextends in spiral lines around the working surface of the roll with afairly steep pitch, which depends upon the workpiece or roll speed andthe axial shift. Its origin during longitudinal grinding comes from anincreased grinding pressure at the cutting edge of the grinding wheelrelative to the following more cylindrical zones thereof. The problemcan be ameliorated by reducing the grinding pressure and changing theratio of the workpiece speed to the axial shift. It can also be helpedby rounding the edge of the grinding wheel.

6. Scratch Patterns

FIGS. 14 a and 14 b show the defect pattern arising in the ground rollin the form of scratch or broken lines or decimal points. The scratchesor points are small depressions in the surface of the roll with amicrogeometric appearance.

The origins of the scratches or broken line defects or points lies inthe penetration of grains from the grinding wheel which breaks loose atthe surface and are pressed into the surface or which derive fromimpurities in the cooling which are pressed into the surface between thegrinding wheel and the workpiece. They may also arise if the grindingwheel is too soft. The solution can be better pressurized flushing ofthe grinding wheel, using a grinding wheel of greater porosity,improvements in cooling, cleaning, changing the cooler, grinding withthe wheel and the workpiece in counterrotation, and/or the use of agrinding wheel with a ceramic pointer.

7. Scale Patterns

FIG. 15 shows a defect state in the form of a scale pattern or, as itmay be known, as an orange pattern. The scale pattern is amacrogeometric deviation of the surface from the truly cylindrical formwith the configuration of scale-like depressions. The depressionsoriginate from vibrations of the truing diamonds during the truingoperations on the grinding wheel resulting from a defective retention orapplication of the diamond to the wheel. Frustoconical diamonds createthe scale pattern. The solution can be better control and mounting ofthe truing operating.

8. Grooving

FIGS. 16 and 16 b show a defect pattern in the form of grooves formed inthe roll surface during the grinding operation. The grooves aremacrogeometric defects in the surface of the roll extendingcircumferentially with a spacing corresponding to the truing spacing.They originate from a truing operation which tends to cut a screw threadprofile into the grinding wheel utilizing a pointed diamond, a highpenetration of the truing tool and a high degree of shift of the truingtool per revolution of the grinding wheel which can be greater than thewear surface of the diamond.

The problem can be reduced by limiting the shift of the truing tool andthe penetration thereof.

9. Cloud-Like Surface Patterns.

FIG. 17 shows this type of defect, which can also be referred to as astreaking or schlieren defect pattern. The cloud-shape covers largeareas in general which are nonuniform deviations in the microgeometry ofthe workpiece or roll surface which only arise in the case of finegrinding and superfinishing of the surface and appear as differences inthe reflectivity of the surface. The origin is aperiodic stiffnessvariations between the grinding wheel and the workpiece which takesplace during the relative movement and appears predominantly with oldermachines or with nonuniform pressure of the grinding wheel or withpressure reduction which may result from use of a next coarser grindingwheel.

The cloud patterns which are produced by aperiodic stiffness differencescannot be easily avoided or removed. They can be minimized by polishingwith very low grinding pressures. The cloud patterns which derive frominefficient grinding pressure reduction must be ground away with coarsergrinding wheels.

10. Large-Area Clearly Delimited Surface Markings.

Such surface markings have been shown diagrammatically with the defectpattern in FIG. 18. Such markings are in the form of deviations from themicrogeometry of the workpiece surface and are visible on finely groundsurfaces as reflection variations with a form which is determined bytheir origin. They can be the result of external effects, for exampleimpacts which slowly diminish the workpiece characteristics like limitedsurface zones with different hardnesses, of machine characteristicslike, for example, gearing interactions, or coolant effects like, forexample. sludge trappings between the grinding wheel and the workpiece.They can be ameliorated by attention to the causes.

The storage of the defect pattern and other typical conditions which cangive rise to defects, as data in memory and the comparison to themeasured signals or images with these defect images enables automaticevaluation as to the cause and can trigger not only the warning but anoutput of data to enable the system to be adjusted to eliminate thedefect. The defect can be automatically eliminated, where appropriate,for example, by a suitable automatic input to the CNC controller.

1. A method of grinding a roll comprising the steps of: (a) mounting aroll for the rolling of workpieces in a roll-grinding machine having agrinding wheel engageable with said roll and grinding a working surfaceof said roll therewith; (b) subsequent to or simultaneously with thegrinding of said working surface of said roll, scanning said workingsurface of said roll for defects with at least one sensor on saidmachine capable of recognizing the geometry of said working surface; (c)then automatically evaluating results of the scanning in step (b) byautomatically comparing the results with stored data as to qualities ofsaid surface; and (d) automatically outputting information as to theevaluation in step (c).
 2. The method defined in claim 1 wherein thestored data includes at least one data set selected from a data set ofdata describing set-point qualities of said working surface and a dataset of data describing typical defects of said working surface.
 3. Themethod defined in claim 2 wherein the scanning is carried out in step(b) with an optical sensor.
 4. The method defined in claim 3 wherein theinformation outputted in step (d) is a warning signal produced when theresult of the evaluation in step (c) indicates a deviation of ameasurement of said surface from the stored data exceeding apredetermined and stored tolerance.
 5. The method defined in claim 4wherein the information outputted in step (d) is displayed graphicallyon a cabinet of the machine.
 6. The method defined in claim 4 whereinthe information outputted in step (d) is displayed in printed form. 7.The method defined in claim 1 wherein the scanning is carried out instep (b) with an optical sensor.
 8. The method defined in claim 1wherein the information outputted in step (d) is a warning signalproduced when the result of the evaluation in step (c) indicates adeviation of a measurement of said surface from the stored dataexceeding a predetermined and stored tolerance.
 9. The method defined inclaim 1 wherein the information outputted in step (d) is displayedgraphically on a cabinet of the machine.
 10. The method defined in claim1 wherein the information outputted in step (d) is displayed in printedform.
 11. A roll-grinding machine comprising: a machine structure forreceiving and rotating a roll for the rolling of workpieces; a grindingwheel engageable with said roll for grinding a working surface of saidroll; at least one sensor capable of recognizing the geometry of saidworking surface for scanning said working surface of said roll fordefects subsequent to or simultaneously with the grinding of saidworking surface of said roll; circuitry connected to said sensor forautomatically evaluating results of the scanning by automaticallycomparing the results with stored data as to qualities of said surface;and a device connected to said circuitry for automatically outputtinginformation as to the evaluation.
 12. The roll-grinding machine definedin claim 11 wherein said sensor capable of recognizing the geometry ofsaid working surface includes a laser.
 13. The roll-grinding machinedefined in claim 12 wherein said sensor capable of recognizing thegeometry of said working surface includes a camera.
 14. Theroll-grinding machine defined in claim 13 wherein said camera is adigital camera.
 15. The roll-grinding machine defined in claim 11wherein said sensor capable of recognizing the geometry of said workingsurface includes a camera.
 16. The roll-grinding machine defined inclaim 15 wherein said camera is a digital camera.
 17. The roll-grindingmachine defined in claim 11, further comprising a digital memoryconnected to said circuit for stored data including at least one dataset selected from a data set of data describing set-point qualities ofsaid working surface and a data set of data describing typical defectsof said working surface.